Abstract: The present invention relates to the demultiplexing of a digital data stream in a receiver so as to retain only those parts of the digital data stream required by the receiver. Such demultiplexing is particularly useful when applied to a receiver circuit in a television system having a digital set-top-box. A memory in the receiver stores packet identifiers of data packets required by the receiver, which are stored in the memory under the control of a first control circuit. A second control circuit extracts packet identifiers from incoming data packets in an input digital data stream. A third control circuit receives the extracted packet identifier and determines whether this matches one of the packet identifiers stored in the memory. A match signal is set by the third control circuit to the second control circuit responsive to a match. The second control circuit demultiplexes the input data packet responsive to the match signal.

Abstract: A controller for controlling direct memory access. Such a controller is particularly applicable when applied to a transport interface in the receiver of a digital set-top-box for television systems. A storage means stores the base and top addresses of a circular buffer in a memory to which received data is to be forwarded and stored, and a write pointer for such buffer is also stored in the storage means. Addressing circuitry generates the address to which the receive data is to be written in dependence on the stored base and top addresses and the write pointer. Output circuitry writes the data into the circular buffer at the location identified by the generated address.

Abstract: An arbiter for arbitrating between a plurality of requests from a plurality of requesters, said arbiter being arranged to assign an order of priority of said requesters, the requester having the highest priority and which has made a request winning the arbitration, wherein the arbiter determines a new priority for said winning requester, said winner being given a priority different from the lowest priority.

Abstract: A circuit and method for scan testing some or all connections to a device, the device under test having at least one output and a plurality of inputs greater than the number of outputs. Such a device typically includes built-in self-test capability. An exclusive-OR gate receives the plurality of inputs and generates an exclusive-OR output. A multiplexer receives the at least one data output and the exclusive-OR as respect inputs, and selectively outputs one of such as a data output. Such selection of the output of the multiplexer is controlled responsive to a scan test signal, the exclusive-OR output being output from the multiplexer in a scan test.